Presently, large-scale exploitation of the coal resource under railroads, water bodies, and constructions have been realized with a backfill mining technique; thus, the coal yield of coal mine is effectively increased, ground surface control is achieved, and the problem of ground waste stacking is solved. In a feeding system for backfill mining, gangues are usually thrown from a level that is higher than the well bottom by hundreds or thousands of meters to the mine shaft bottom. Thus, when the gangues reach to the mine shaft bottom, the speed of the gangues is usually more than 100 m/s. The high-speed gangues have huge impact force, and may cause severe damage to the wall of down-hole storage silo when they reach to the mine shaft bottom if they are not cushioned; consequently, the service life of the storage silo may be shortened, and waste of resource may occur.